Posterior lumbar dynamic stabilization instead of arthrodesis for symptomatic adjacent-segment degenerative stenosis: description of a novel technique.

OBJECTIVE The development of symptomatic adjacent-segment disease (ASD) is a well-recognized consequence of lumbar fusion surgery. Extension of a fusion to a diseased segment may only lead to subsequent adjacent-segment degeneration. The authors report the use of a novel technique that uses dynamic stabilization instead of arthrodesis for the surgical treatment of symptomatic ASD following a prior lumbar instrumented fusion. METHODS A cohort of 28 consecutive patients was evaluated who developed symptomatic stenosis immediately adjacent to a previous lumbar instrumented fusion. All patients had symptoms of neurogenic claudication refractory to nonsurgical treatment and were surgically treated with decompression and dynamic stabilization instead of extending the fusion construct using a posterior lumbar dynamic stabilization system. Preoperative symptoms, visual analog scale (VAS) pain scores, and perioperative complications were recorded. Clinical outcome was gauged by comparing VAS scores prior to surgery and at the time of last follow-up. RESULTS The mean follow-up duration was 52 months (range 17-94 months). The mean interval from the time of primary fusion surgery to the dynamic stabilization surgery was 40 months (range 10-96 months). The mean patient age was 51 years (range 29-76 years). There were 19 (68%) men and 9 (32%) women. Twenty-three patients (82%) presented with low-back pain at time of surgery, whereas 24 patients (86%) presented with lower-extremity symptoms only. Twenty-four patients (86%) underwent operations that were performed using single-level dynamic stabilization, 3 patients (11%) were treated at 2 levels, and 1 patient underwent 3-level decompression and dynamic stabilization. The most commonly affected and treated level (46%) was L3-4. The mean preoperative VAS pain score was 8, whereas the mean postoperative score was 3. No patient required surgery for symptomatic degeneration rostral to the level of dynamic stabilization during the follow-up period. CONCLUSIONS The use of posterior lumbar dynamic stabilization may offer a valid and safe option for the management of patients who develop ASD rostral to a previously instrumented arthrodesis. The technique may serve as an alternative to multilevel arthrodesis in this patient population. By implanting a dynamic stabilization device instead of an extension of a rigid construct, this might translate into a reduction in the development of yet another level of ASD.

Evaluation of Clinical and Histologic Effects of High-Dose Radiosurgery on Rat Dorsal Root Ganglion.

BACKGROUND: Stereotactic radiosurgery (SRS) is an effective technique to create lesions of the trigeminal nerve to treat refractory trigeminal neuralgia. In the lumbar spine, the dorsal root ganglion (DRG) contains the body of the sensory neurons responsible for pain sensitivity. Neuromodulation of the DRG might therefore improve chronic peripheral pain. This study was performed to determine the feasibility, clinical, and histologic effects of delivering high-dose SRS targeted to the lumbar DRG in a rat model. METHODS: Four Sprague Dawley male rats underwent 80 Gy maximum-dose single-fraction SRS to the left L5 and L6 DRG using the Leksell Gamma Knife Icon (Elekta, Atlanta, Georgia, USA). The right L5 and L6 DRGs served as controls. The animals were evaluated for motor and sensory deficits every 2 weeks and were sacrificed at 3 and 6 months after SRS. Common histologic techniques were used to assess for fibrosis and demyelination at the target levels. RESULTS: No detectable motor or sensory deficits were seen in any animal. Histologic changes including fibrosis and loss of myelin were noted to the left L5 and L6 DRGs, but not the right side control DRGs. Fibrotic changes within the vertebral body were also evident on the treated sides of the vertebral bodies. CONCLUSIONS: We were able to detect a demyelinating response from SRS delivered to the DRG in rats. Because such changes mimic those seen after trigeminal SRS in experimental animals, we hypothesize that radiosurgery may be a potential option in chronic spinal radicular pain amenable to neuromodulation.

A Longitudinal Cohort Investigation of the Development of Symptomatic Adjacent Level Compression Fractures Following Balloon-assisted Kyphoplasty in a Series of 726 Patients.

BACKGROUND: Balloon-assisted kyphoplasty (BAK) is a well-accepted treatment for symptomatic vertebral compression fractures (VCF) secondary to osteoporosis. Some have raised a concern of an increased incidence of adjacent fractures due to alterations in spine biomechanics after cement augmentation. The incidence of subsequent VCFs following BAK is poorly understood. The aim of this study was to investigate the timing, location, and incidence of new VCFs following BAK and to identify risk factors associated specifically with the occurrence of new adjacent level fractures. OBJECTIVES: The study was performed to determine the incidence of symptomatic subsequent adjacent and remote level compression fractures in a cohort of patients undergoing BAK. STUDY DESIGN: Longitudinal cohort investigation at an academic medical center and a central referral center for VCFs. SETTING: A consecutive single surgeon series of 726 patients with osteoporotic compression fractures. METHODS: A prospectively collected cohort of 726 patients who underwent BAK between 2001 and 2014 for osteoporotic VCFs was evaluated. Seventy-seven patients were identified who underwent a second BAK for a new compression fracture and were include in the present series. The indication for BAK treatment was pain unresponsive to non-surgical management for all cases. Variables were recorded for each patient, including the time between index and subsequent fracture, fracture level, and number of initial fractures as well as with tobacco use, body mass index (BMI), and chronic steroid use. RESULTS: Seventy-seven of 726 patients (10.6%) underwent a second BAK procedure on average 350 days following the initial procedure (range 21 to 2,691 days). Third and fourth procedures were less common, treated in 11 and 3 patients, respectively. Forty-eight of 77 patients (62%) suffered a fracture at a level immediately adjacent to the index level at mean time of 256 days. Remote level fractures were treated at a mean time of 489 days, but no statistical difference was noted. There was no statistically significant difference between tobacco use, BMI, and chronic steroid use between patients suffering from remote and adjacent level VCFs. LIMITATIONS: This was not a population based study, and the true incidence of subsequent fractures after BAK might be underestimated by this analysis. CONCLUSIONS: Symptomatic compression fractures after BAK are relatively uncommon and may occur long after the initial kyphoplasty procedure. Only half of subsequent fractures occur immediately adjacent to the initially treated level; the others occur remotely. Patients with a single symptomatic thoracic or lumbar fracture suffered from remote and adjacent level fractures equally. In contrast, all patients who suffered both a thoracic and lumbar fracture at the same time had a second fracture at an adjacent level. Specific risk factors for remote versus adjacent level fractures could not be determined. Key words: Balloon kyphoplasty, cement augmentation, osteoporosis, vertebral compression fracture, adjacent level fracture, vertebroplasty.